Terahertz (THz) lasers produce light of frequency in the range of 0.3 to 4 Terahertz with wave lengths in the range of 75 μm to 1000 μm and are useful at power ranges from 0.02 to 2 watts. These lasers reflect from metals and some organic molecules and are absorbed by water and some polar molecules. The light transmits through clothing, paper, and packaging materials including plastic and cardboard with varying degrees of efficacy depending on wavelength.
The reflectivity from metals and certain explosives, low power and ability to penetrate clothing makes Terahertz lasers a good candidate for remote sensing of weapons on people but heretofore no one has succeeded in producing a device that is effective and compact.